For most Brits, most of the time they're one and the same - the taxman will tell your employer your tax code (= your tax free amount) and it's usually the same

For most Brits, most of the time they're one and the same - the taxman will tell your employer your tax code (= your tax free amount) and it's usually the same offset from standard each year. From this thread it appears that American taxes have more complicated rules.